As is well known, flat panel displays (hereinafter, simply referred to as FPDs) have become mainstream as image display devices in recent years, the FPDs being typified by a liquid crystal display (LCD), a plasma display (PDP), a field emission display (FED), an OLED display (OLED), and the like. Progress is being made toward reducing the weight of those FPDs, and hence glass substrates used for the FPDs are also currently becoming thinner.
Further, for example, organic light-emitting diodes are used not only to flicker three fine primary colors with TFTs as in displays, but also to emit monochromatic light (for example, white color light), and hence the organic light-emitting diodes are beginning to be used also as flat surface light sources such as a backlight of an LCD and a light source of an indoor lighting device. Further, in a lighting device using organic light-emitting diodes, the shape of its light-emitting surface can be freely changed if flexibility can only be imparted to a glass substrate. Thus, from the viewpoint of securing sufficient flexibility, progress is also being made toward formation of a very thin plate glass (formation of a glass film) in manufacturing a glass substrate used in the lighting device of this kind.
Here, for example, Patent Literature 1 described below proposes, as a process for manufacturing a belt-like glass having a thin plate shape, a so-called glass film, a technology which involves forming a glass film ribbon having a thickness of 30 μm to 2,000 μm by a down-draw method, in particular, a slot down-draw method, drawing the glass film ribbon vertically downward, bending (inflecting) the glass film ribbon in the horizontal direction, cutting off both ends of the glass film ribbon by using a laser, and then cutting the glass film ribbon into a piece having a predetermined length, thereby providing a glass substrate having a predetermined size. Patent Literature 1 also describes that a glass film ribbon having a thickness of 30 μm to 400 μm can be wound (by using predetermined rollers or the like) after its both ends are cut, without being cut into a piece having a predetermined length.
Moreover, Patent Literature 2 proposes a technology which involves forming a glass film ribbon having a thickness of less than 0.7 mm by a so-called float process, trimming both end portions in the width direction of the glass film ribbon on a molten tin bath, and winding the resultant glass film ribbon into a roll shape.
As described above, a glass film ribbon can be wound into a roll shape by taking advantage of its excellent flexibility unlike conventional glass substrates, and hence the glass film ribbon can be supplied to a production system such as a roll-to-roll manufacturing method.